The present invention relates to the assembly of wheels for automotive vehicles, and more specifically to a new apparatus and method for mounting a valve stem on a wheel rim.
The great majority of wheels produced for automotive vehicles include a metal rim, a tubeless tire mounted on the rim, and a valve stem which projects through a hole in the rim to communicate with the interior of the tire and permit inflation.
In the past, automobile wheels have been assembled utilizing primarily manual labor. In particular, the mounting of the valve stem to the rim has been accomplished by a hand-held stem inserter tool such as that disclosed in U.S. Pat. Nos. 3,852,839 and U.S. Pat. No. 4,807,343. Similarly, the mounting of the tire on the rim has involved a worker placing the rim in a fixture, positioning the tire partially over the rim, and actuating a machine which then presses the tire downwardly into position around the rim. Such manual processes are expenses because of the labor and time involved, and are subject to human error which may produce defective wheels.
It is desirable to adapt modern robotic and machine vision systems to automate the manufacture of mounted tires.
It is an objective of this invention to provide a method and apparatus for the high volume, low cost assembly of valve stems to wheel rims. It is a further objective of this invention to provide a completely automated method and apparatus utilizing a robotic manipulator to handle the rim during assembly.
It is a further objective of this invention to provide an automated assembly apparatus and method adapted to handle different types and sizes of rims having valve stem mounting holes at different locations and aligned at different angles.
The present invention is intended for use with both normal sized and miniature rims (such as those used for compact spares on some vehicles) having a hole passing therethrough for receiving a tubular valve stem. According to the invention, the rim is positioned in a gauging station where the location and alignment of the hole is determined. A robotic manipulator grasps the wheel in the gauging station and, under the direction of an electronic control system, moves the rim to a mounting station where a valve stem is retained. The manipulator positions the rim such that the hole is in alignment with the longitudinal axis of the valve stem, and the valve stem and the wheel are then moved relative to one another to insert the valve stem through the hole in the rim.
According to a preferred embodiment of the invention, the gauging station utilizes a machine vision system to determine the radial and circumferential location of the hole on the rim and the angle which the central axis of the hole makes with the central axis of the rim. These factors may be determined, at least in part, by programming the machine vision system to recognize certain features of the rim which identify it as being an example of one of a plurality of pre-programmed types of rims. The hole location and/or alignment information for each type of rim is stored, and need not be directly measured by the machine vision system. The data describing the location and alignment of the hole is relayed to the control system so that it can direct the robotic manipulator to properly position the rim in relation to the valve stem at the mounting station.
According to another feature of the invention, the automated assembly apparatus includes a plurality of mounting stations, each containing a different type of valve stem. The machine vision system identifies a rim as being an example of one of the plurality of pre-programmed types and directs the robotic manipulator to move the rim to the correct mounting station and insert the valve stem into the hole in the rim. This allows the assembly apparatus to simultaneously handle different types and/or sizes of rims and mount the appropriate type of valve stem to each rim.
In an alternative embodiment of the invention, the gauging station comprises a rotating table for receiving the wheel and rotating it about its central axis, and an xe2x80x9celectric eyexe2x80x9d optical sensor which directs a bear of infrared light onto the rim. As the rim rotates through the beam, the presence or lack of a reflection of the light beam is used to detect the location of the hole, and rotation of the table is stopped when the hole is in alignment with the beam. If desired, a probe mounted on the gauging station may be extended to project into the hole to confirm that the hole is at the desired position and, if necessary, reposition the rim slightly to provide a precise positioning of the hole. In this embodiment of the gauging station, the hole is always in the same position relative to the gauging station when the robotic manipulator grasps the rim prior to moving it to the mounting station.
According to another feature of the invention, a power-actuated nut runner is used to tighten a nut over a threaded portion of the valve stem to secure it in connection with the rim. In one possible embodiment of the invention, the nut runner is mounted on the robotic manipulator. In an alternative embodiment, the nut runner is mounted on or adjacent to the valve stem mounting station.
According to another feature of the invention, a sorting and conveying apparatus is disposed on or adjacent the mounting station and supplies a continuous stream of valve stems for mounting to rims which are passed in sequence to the mounting station by the robotic manipulator.
In the preferred embodiment of the invention, the valve stem is held substantially stationary relative to the mounting station and the robotic manipulator urges the wheel onto the valve stem. It has been found that this method of inserting the valve stem through the hole provides for an accurate, positive, and repeatable insertion of the valve stem into the hole.
In yet another feature of the invention, the robotic manipulator transfers the assembled rim and valve stem from the mounting station to a subsequent work station and releases the rim with the valve stem in a consistent, desired reference position relative to the work station. This allows subsequent assembly steps to be performed on the rim, such as mounting of a tire, to be accomplished with reference to the position of the valve stem on the rim.